This element of design is Negative Space. The hand isn't actually holding anything. It implies that there is a light bulb in the empty space. Negative space guides your imagination to finish the image.
WHITE SPACE: I love the simple style of this poster and how an image is made just using the hand and the screw. I think that it works well with the space and there is a focus point in the middle of the design.
Self portrait ideas Mapping 2013 on Behance Use a process like this for "identity/self-concept" activity about skin color/shade/tone/palette. Put vertical photo strip of every child together on a couple images to make a collective face.